Filter



H. CHAFFEY June 6, 1950 FILTER Filed Feb. 2, 1948 I I Invenlm' Patented June 6, 1950 FILTER Reginald Herbert assignor to Vokes Chaifey, Guildford, England, Limited, Guildford, England Application February 2, 1948, Serial No. 5,763

In Great Britain May 30, 1947 4 Claims.

In the manufacture of filters in which a filtering medium such as felt or suitable textile material (hereinafter included when felt is referred to) is supported on a stiffer medium, there have been various arrangements for making a joint at the edges. For instance, in a deeply pleated or star-shaped element in which felt is carried by wire gauze, the marginal portions of the felt have been turned over the edges of the gauze and secured by a row of stitching run through the two layers of felt and the intermediate layer of gauze. For many purposes this is satisfactory, but where the filter has to withstand a considerable difference of pressure, the ordinary wire gauze is somewhat inclined to deform. In such circumstances, also, such stitching may be undesirable because the holes made by the passage of the needle in stitching to wire gauze the type of felt used to give fin filtration with considerable back pressure are not always negligible.

The present invention is designed to provide an effective edge joint applicable where the felt is supported on wire gauze but more especially intended to enable perforated metal to be effectively used as the supporting medium.

The main idea underlying the invention is the use of stitching at or outside the edge of the supporting medium to produce a roll or bead or pipe of the filtering medium at the bend where it is turned over the edge of the supporting medium.

Typical forms of the invention are illustrated by the accompanying drawings in which:

Figure 1 shows in elevation, partly sectioned, a filter unit adapted for filtration of fluid passing from inside to outside,

Figure 2 is an underside plan of the same,

Figure 3 is a fragmentary detail to much enlarged scale, and

Figure 4 is a view similar to Fig. 3 of a modified form.

The unit shown in Figs. 1 and 2 is of wellknown type in which a star-shaped filtering element I (Fig. 2) is clamped between end caps 2 and 3 by means of a nut 4 engaging a screw 5 carried by a spider 6. The fluid to be filtered enters at inlet 7 and in case of excessive resistance to its passage due to clogging of the filtering element, the element moves downwardly, away from its operative position against the upward pressure of a spring and the fluid is bypassed through the ports 8.

The star-shaped element l is formed from a support ll of perforated sheet material with the felt [2 turned over both its edges with a line of stitching l3 running along about an eighth of an inch or less from the bend in the felt, so that the edge of the perforated sheet ll lies against a row of stitching l3 between the main part of the felt and the turnover lZa, which may conveniently extend about half an inch. A length of the combined material can then be crimped or pleated in known fashion and bent round and joined to make a. star-shaped element as shown or used as a panel, as in the case of the ordinary stitchedon felt and wire gauze.

The piping at the edges, when compressed, makes an excellent joint of fairly substantial width (see Fig. 3) and the compression ensures that the needle holes are not exposed as when the felt is stitched to a, wire gauze.

A similar arrangement can be used as shown at Fig. 4 with wire gauze l4, the cut ends I5 of the wire of the gauze being preferably turned in to make an edge that will lie snugly against the piping.

In either case a suitable binding or edging l6 of suitable material such as soft metal or rubber or plastic material may be applied to the edges of the supporting medium before the felt is bent over them if desired. The piping can also be filled with or an internal dressing of latex or other suitable material used at the bend if desired in particular cases. Normally, however, the joint in itssimple form should be satisfactory.

It will be noted that the invention, from one aspect, provides a filtering screen in which perforated metal supports the filtering medium and a piping of the filtering medium is arranged to form joints at the edges.

I claim:

1. A filter element comprising a stiff foraminous sheet support and a, sheet of filter medium on one side of said support, the opposite edges of said filter sheet being folded over and stitched adjacent the folds to define channels removably surrounding the coinciding edges of said support.

2. A filter element as defined in claim 1 wherein said support comprises a perforated sheet.

3. A filter element as defined in claim 1 wherein said support comprises a wire gauze.

4. A filter element as defined in claim 1 wherein an edging strip is applied around the edges of said support to protect said channels from abras1on.

REGINALD HERBERT CHAFFEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,220,297 Vanderhoof Mar. 27, 1917 FOREIGN PATENTS Number Country Date 137,471 Austria May 11, 1934 

